Sediment yield variability in the Upper Yangtze, China

The development and increasing availability of global environmental data se ts provides an opportunity to examine systematically the relationship betwe en sediment yields and controlling catchment variables, employing Geographi cal Information Systems. Few studies have attempted to harness such informa tion to analyse variations in sediment yields within large catchments. Sedi ment yields from 62 long-term gauging stations within the catchment of the Upper Yangtze River, China, have been analysed in relation to variables des cribing hydrology, climate, topography and population density. This analysi s is particularly significant as the 10(6) km(2) catchment area of the Uppe r Yangtze will shortly be impacted by the world's largest dam scheme (the T hree Gorges Project). There is a high degree of scatter in sediment yields because of natural diversity in the catchment, but this scatter is reduced when the data are grouped according to tributary location, catchment size a nd maximum elevation. Sediment yields generally increase with precipitation , runoff and population density and decrease with elevation, but there is e vidence of scale dependency and of variation between geographic regions wit hin the basin. The small number of variables used are capable of explaining the majority of variance in the comparatively 'natural' western tributarie s but are less adequate in areas affected by large-scale agricultural activ ity. in future, improvements in the resolution and accessibility of environ mental data sets will allow more detailed analysis of regional variability in sediment yield. Copyright (C) 1999 John Wiley & Sons, Ltd.